FWIW, I found the same thing SnS :)
There is a mathimatical difference in your drop down "level" as well.
If you were vaping 24mg and dropped to 18mg, you cut your nic intake by 25%
If you were vaping 12mg and dropped to 8mg, you cut your nic intake by 33.333333333333333333333333333333 %
So...